Solucion de un sistema de ecuaciones c++

#include<stdio.h>
#include<conio.h>
#include<iostream.h>
int splash()
{
gotoxy(6,4); cout<<"____________________________________________________________

__________";
gotoxy(6,5); cout<<"* * * * * * * * * * * * * * * * * * * * * * * *";
gotoxy(6,7); cout<<"* * * * * * * OO OO OOOOOO OOOOOO * * * * * **";
gotoxy(6,8); cout<<"* * * * * * * OO OO OO OO OOOOOO * * * * * * *";
gotoxy(6,9); cout<<"* * * * * * * OO OO OO OO OO * * * * * * *";
gotoxy(6,10); cout<<"* * * * * * * OO OO OOOOOO OO * * * * * * *";
gotoxy(6,11); cout<<"* * * * * * * OOOOOO OO OO * * * * * **";
gotoxy(6,12); cout<<"* * * * * * * OOOOOO OO OO * * * * * * *";
gotoxy(6,14); cout<<"* * * * * UNIVERSIDAD POLITECNICA DE TLAXCALA * * * * * *";
gotoxy(6,15); cout<<"____________________________________________________________

__________";
getch(); clrscr();
gotoxy(6,4);cout<<"____________________________________________________________

__________";
gotoxy(6,5); cout<<"**********************************************************************";
gotoxy(6,7); cout<<" MATSOLUTION V2.0 ";
gotoxy(6,9); cout<<" LICENCIA: GPL";
gotoxy(6,11); cout<<" AUTORES:";
gotoxy(6,12); cout<<" +Eduardo MelendezSanchez";
gotoxy(6,13); cout<<" +Sonia Luna Suarez";
gotoxy(6,14); cout<<" +Natali Covarrubias";
gotoxy(6,15); cout<<" +Aide Cortes";
gotoxy(6,16); cout<<" +Andres Ivan";
gotoxy(6,18); cout<<" Dudas o comentarios: Eduardo1025@melendez.mitmx.net";
gotoxy(6,20);cout<<"**********************************************************************";
gotoxy(6,21); cout<<"____________________________________________________________

__________";
return 0;
}

int menu() //funcion para imprimir menu
{
int op;
clrscr();
gotoxy(10,2); cout<<" BIENVENIDO AL PROGRAMA PARA LA SOLUCION DE MATRICES"<<endl; //gotoxy(x,y)-->> fucion de posicion.
gotoxy(10,3);cout<<"±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±"<<endl;
gotoxy(10,5); cout<<" M E N U";
gotoxy(10,6); cout<<" ********************************";
gotoxy(10,7); cout<<" Resolver matriz: * [1] Matriz no Homogenea (3x3)*";
gotoxy(10,8); cout<<" * [2] Acerca de.. *";
gotoxy(10,9); cout<<" * [3] SALIR*";
gotoxy(10,10);cout<<" ********************************";
gotoxy(10,14);cout<<"±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±";
gotoxy(10,12);cout<<" Tu opcion es: ";cin>>op;
return (op);
}

int matnh() //funcion para resolver matriz
{
float mat[10][10];
floatmataux[3][4],aux,aux2;
int i,j,x,y,a=1,b;
clrscr();
gotoxy(4,2); cout<<"A continuacion introduce los valores de la matriz:";
gotoxy(10,5); cout<<"| | |";
gotoxy(10,6); cout<<"| | |";
gotoxy(10,7); cout<<"| | |";
x=12;
y=5;
for(i=0;i<=2;i++) //lee los valores de la matriz....
{
for(j=0;j<=3;j++)
{gotoxy(x,y);cin>>mat[i][j];
x+=5;
}
y++;
x=12;
}
gotoxy(22,10); cout<<"| | |";
gotoxy(22,11); cout<<"| | |";
gotoxy(22,12); cout<<"| | |";

/*PASO 1 R1 PIVOTE*/
gotoxy(10,10); cout<<"R1/"<<mat[0][0]; //mensaje de operacion
aux=mat[0][0];
x=23;
for(i=0;i<=3;i++)...